what are waves? waves = a transfer of energy from one place to another ex. = a water wave is a...
TRANSCRIPT
What are waves?
• Waves = a transfer of energy from one place to another
• Ex. = a water wave is a disturbance at the surface of the water.
• Ex. = a seismic wave is a moves through through the soil of earth
Can waves provide energy?
• Both of the previous waves can transfer their energy
• Water waves can move a boat up and down – this requires work (energy)
• Seismic waves can move a building back and forth and up and down
What about sound waves?
• Sounds waves transfer energy with air pressure
• The sound travels outward in all directions from the source
• When it reaches your ear, it does work by moving your ear drum
Mechanical waves
• Everything we mentioned are described as mechanical waves
• These require a medium, such as water, air, even a rope or spring
Wave terms• Wave pulse –
produced if a source makes a single disturbance (like a bang)
• Period wave – if the source vibrates repeatedly, like a guitar string
Transverse wave• Particles in the medium,
like a rope, move up and down, but the wave moves back and forth.
Longitudinal wave• Particles move back
and forth as well as the wave, like in a slinky spring
• Peak – each of the highest points of a wave
• Trough – each of the lowest points of a wave
• Amplitude – the distance from peak to trough divided by 2
Wavelength
• The wavelength is the length of the repeating pattern
• Could be from peak to peak
Frequency
• Frequency is number of waves that pass a certain point per unit of time
• We call this Hertz (Hz)
Period of wave
• The period is the time it takes just one wavelength to pass a point
Wave speed = how fast it moves
Speed will affect frequencyWatch this:
Calculating wavelength, Frenquency & Wave Speed
• f = 1/T where T is the period or time for 1 wave
• Remember speed = distance / time– What is our distance for waves? – What is our time?
• Wave speed = wavelength/period– V = /T we can substitute in f for 1/T
– To get: v = f *
Calculating wavelength, Frenquency & Wave Speed
• Example – The string of a piano that produces the note middle C vibrates with a frequency of 264 Hz. If the sound waves produced by this string have a wavelength in air of 1.30m, what is the speed of sound in air?